Race for the Galaxy! It's so much fun, though I found the rules to be difficult to understand at first. http://www.amazon.com/Rio-Grande-Games-RGG301-Galaxy/dp/B000...
Our daughter's almost 10, and with the exception of Twilight Imperium (this game is massive, especially when you add both expansions) plays them all with us. In addition to spending more time together as a family, I'd say it's helped a with her math, reading, and critical thinking.
My son's almost four and I can't wait for him to want to play all these games.